Dithiazine dioxides having alkyl substitution at the S have already been described, a biological activity has not been mentioned (see Nakahashi, K. et al., Bull. Chem. Soc. Jpn. 45, 3217 (1972); Masegawa, K. et al., Bull. Chem. Soc. Jpn. 45, 1567 (1972)).